CAMBRIDGE - Charlie Bruno was, by all accounts, the one guy in his college dormitory who would do just about anything on a lark. On the MIT campus during the anything-goes early 1970s, he was one of the first to go streaking. He once built a homemade rocket and shot it into the Charles River, friends say.

But it was his piano work that still resounds at Baker House, the iconic Massachusetts Institute of Technology dormitory along Memorial Drive. Not that he played, rather, in November 1972, Bruno decided it would be hugely entertaining to heave an unplayable old upright off the sixth-floor roof of the residence hall.

Although no one could have known at the time, the inaugural Baker House Piano Drop would become an annual event, more or less, and one of the best known of the college’s long legacy of famous pranks, or hacks. After a hiatus in the 1980s, the prank was moved to coincide with Drop Day, the last day students can drop classes during the semester. This year’s piano drop, scheduled to take place Thursday, marks the 40th anniversary of the uniquely MIT cultural oddity.

The drop occurs over an enclosed section of lawn on the Memorial Drive side of Baker House, where the piano crashes and splinters on plywood sheets laid over the grass. In the aftermath, onlookers take home souvenir shards of the mangled instrument.

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“The pianos find us,’’ said Michael Plasmeier, the current Baker House president, sitting in the dorm lobby on a recent day.

This year, he said, the dorm was contacted by a donor who had five baby grands ready for the junkyard. The man was happy to provide the pianos, as long as the students took all five off his hands, even though they require only one.

“Right now we have two pianos chilling downstairs and two more on the loading dock,’’ said Jonathan Wang, this year’s Piano Drop chairman.

The students go through mandatory safety training and must wear harnesses on the roof to prevent them from falling, explained Wang, a 20-year-old from Florida studying in the electrical engineering and computer science department.

When the first piano hit the pavement on the other side of the building in 1972, the sound was not exactly show-stopping music.

“It sounded like a big bang; that’s it,’’ said Bill Short, an MIT graduate who made a short film of the first piano drop. “It was a heavy thing hitting the pavement. There was nothing musical about it.’’

Bruno, who died at age 49 in 2001, had a well-earned reputation for mischief.

“He would do pretty much anything,’’ recalled Trip Barber, a fellow Baker House resident at the time who now does operations analysis for the US Navy. Bruno, an aeronautical engineering student, dreamed of being an astronaut, his friend said.

This being MIT, they named a unit of measurement after him: a Bruno is a unit of volume resulting from a piano falling six stories.

EVAN RICHMAN/GLOBE STAFF/FILE 2008

Student Aziz Albahar checked the damage after a baby grand was dropped onto another piano in 2008.

In the aftermath of the 1960s, there was a reckless spirit among college students all over. Phone hacks were big at the time, as several MIT graduates recalled; one Baker House resident, a mountain climber, once scaled the side wall.

“There were some pretty crazy guys in the group,’’ said Andrew Celentano, a former Baker House president who went on to work for IBM before starting his own consulting business.

Celentano also plays piano and kept a Farfisa organ and, later, an upright piano in his room at Baker House. He occasionally plays the piano in the lounge at Symphony Hall. “It’s a beautiful Steinway grand,’’ he said, “and of course I’d never want any harm to come to it.’’

Kevin Struhl, a biological chemist at Harvard who graduated from MIT in 1974, was another Baker House resident on hand for the first drop. There was no grand purpose to it, he said.

““I think people just thought it was a cool thing to do,’’ he said. “It was not that creative, just a goofy, stupid thing to do, and I sort of agree.’’

This year, Plasmeier said, Baker House residents have a bit of a challenge because the launching rig they use is designed more for upright pianos than grands. Other than that, there’s not a whole lot to it.

“You just roll the piano into the elevator and hit the R button,’’ he said.

And once it’s on the roof, said Wang, “you’ve just got to let gravity do its work.’’

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